1. Field of the Invention
The present invention relates to a projection type display apparatus using a light valve. Further, the present invention relates to a projection type display apparatus comprising a light source, at least one optical element and a projection lens.
2. Description of the Related Art
A projection type display apparatus comprises a light source, a light valve such as a liquid crystal panel and a projection lens, in which the image light formed by the light valve is projected onto a screen by the projection lens thereby to form an enlarged image on the screen. A projection type color display apparatus, on the other hand, comprises a light source, color separation means for separating the light of the light source into color light beams of red, green and blue, a plurality of light valves for modulating each of the separated color light beams, color synthesizing means for synthesizing the image light beams formed by a plurality of the light valves into one synthesized light, and a projection lens for projecting the synthesized light.
The projection type display apparatus includes a housing, and all the members described above are arranged in the housing. The housing shields the light so that no light other than the light projected from the projection lens leaks out. The light source and the light valves generate heat. If the heat remains in the housing and the internal temperature increases, the operation of the parts is adversely affected. In view of this, one intake fan and one exhaust fan are arranged in the housing so that cooling air flows in the housing.
The cooling air flowing in the housing cools the light valves and the polarizers which generate considerable heat mainly due to the absorption of light, and is further adapted to cool other heat generating members such as the power supply, the light source and the ballast. With the trend of miniaturization of the projection type display apparatus, however, the increased density of the members arranged in the housing and the increased light density and light fluxes, to meet the required image clarity, tends to increase the amount of heat generated in the housing. For this reason, it has become difficult for the single intake fan and the single exhaust fan to efficiently circulate the cooling air to reach all the heat generating members. It has thus become necessary to arrange a plurality of large capacity intake fans in the vicinity of the light valves, the light sources and all other heat generating members, respectively, to supply fresh air directly to each heat generating member.
The color separation means and the color synthesizing means are configured with dichroic mirrors. Each of the dichroic mirror and the total reflection mirror is held to a fixed structure by a holding member. For supporting the mirror, for example, a support plate having a rectangular opening is used. The mirror is larger than the rectangular opening, and is arranged on one surface of the support plate while covering the rectangular opening. The support plate includes two holding members for holding the mirror at the two opposed sides thereof, and each holding member is an elongated fitting extending along each side of the mirror. The support plate is mounted to a pair of bases extending in the direction parallel to the light path.
In the configuration with a plurality of large capacity intake fans arranged in the vicinity of all the heat generating members including the light valves and the light source, respectively, to supply fresh air directly to each heat generating member, the intake fans are arranged at a plurality of positions in the housing, and intake holes are required at a plurality of positions in the housing. This poses the problem of light leaking out of the housing. Also, a plurality of the intake fans constitute a noise source and, in the resulting apparatus, noise is a crucial problem.
Also, in the case where the light source including a lamp and a reflector is cooled, the cooling air should be led to the front side of the reflector to cool the lamp directly. However, cables and the like are arranged on the rear side of the reflector, and it has been found that the cables and the like must not be overheated as it has an undesirable effect. Also, the light source is desirably arranged in the housing replaceably, and the cooling unit for the light source desirably is adapted to meets the requirements of the replacing the light source.
Also, regarding the dichroic mirrors and the total reflection mirrors of the color separation means and the color synthesizing means, the elongated holding members hold the mirror between the holding member and the support plate. If the support plate or the holding members, which are to be flat, are warped, the problem is posed of a distorted mirror. In other words, two straight lines not parallel to each other cannot form one plane and thus cause a distortion in the mirror. The distorted mirror distorts the direction in which the light is reflected on the mirror, thereby leading to the problem of variations in the characteristics of the optical system. A similar problem is encountered when arranging a mirror between the projection lens and the screen. For this reason, in the prior art, the thickness of the mirror is increased and the strength of the support plate is also increased while at the same time increasing the accuracy thereof to prevent mirror distortion. This method, however, increases the weight of the mirror and the support member for an increased mirror cost.
Further, the following problem is posed.
A projection type liquid crystal display apparatus comprises a light source, a liquid crystal panel having a substantially rectangular display portion, a projection lens and a pair of polarizers arranged on the opposite sides of the liquid crystal panel. The light emitted from the light source is linearly polarized by the polarizer on the light incidence side and enters the liquid crystal panel. The light is spatially modulated in the liquid crystal panel based on the image information. The light emitted from the liquid crystal panel is projected by the projection lens through the polarizer on the light emission side. Also, a condenser lens is arranged before the polarizer on the light incidence side. In the case of a projection type liquid crystal display apparatus for color display, three sets of liquid crystal panels, polarizers, condenser lenses and color separation and synthesizing members are arranged.
For increasing the brightness of the projection type liquid crystal display apparatus, the amount of light entering the polarizer and the liquid crystal panels must be increased. In the case where the light amount entering the polarizers and the liquid crystal panels, however, the problem is that the polarizers and the liquid crystal panels generate heat due to light absorption. Assuming that the light source is a 350 W metal halide lamp, for example, the amount of light (energy) entering the polarizer on the light incidence side after color separation is about 8 W, of which about 50% is absorbed into the polarizer on the light incidence side, so that the heat of about 4 W is generated in the vicinity of the liquid crystal panels.
The polarizers and the liquid crystal panels are generally cooled by air. Specifically, the air is sent into the projection type liquid crystal display apparatus by fan, so that the cooling air cools the polarizers and the liquid crystal panels. The polarizers and the liquid crystal panels are efficiently cooled as the cooling air passes through the space between the polarizer and the liquid crystal panel in the direction substantially parallel to the surface of the polarizer and the liquid crystal panel.
Japanese Unexamined Patent (Kokai) No. 2-168697 discloses a radiation fin having an oblique protrusion arranged in a duct thereby to generate a main air flow substantially straight along the duct and a subsidiary air flowing along the duct ceiling and directed downward. The heat generating members to be cooled, however, are arranged on the bottom of the duct, and the air generally flows in a predetermined direction along the surface of the heat generating members.
Japanese Unexamined Patent (Kokai) No. 8-29874 discloses a projection type liquid crystal display apparatus comprising a rectifier fin inserted between a polarizer and a liquid crystal panel, in which the cooling air is blown between the polarizer and the liquid crystal panel.
In the projection type liquid crystal display apparatus, a superior cooling operation can be performed by sending the cooling air in the direction substantially parallel to the surface of optical elements such as the polarizer and the liquid crystal panel. With the increase in brightness of the projection type liquid crystal display apparatus, however, a cooling means capable of more effective cooling is desired.
An object of the present invention is to provide a projection type display apparatus capable of appropriately cooling internal heat generating members with only a little light leakage and low noise.
A projection type display apparatus according to the present invention comprises a housing, at least one light valve arranged in the housing for forming an image light, a projection lens arranged in the housing for projecting in enlarged form the image light formed by said at least one light valve, at least one heat generating member arranged in the housing, at least one first fan for introducing cooling air into the housing so that the cooling air comes into contact with said at least one light valve, at least one second fan arranged in the housing so that the cooling air comes into direct contact with said at least one heat generating member, and at least one third fan for exhausting the cooling air out of the housing.
In view of this, an air intake fan is provided for the light valve of each color of R, G, and B and the light valves are individually cooled. These three fans are sirocco fans high in air resistance, and arranged on the bottom of the apparatus as intake fans for the apparatus. The housing has at least an air inlet in the bottom portion thereof. By concentrating the air inlets in the bottom portion of the housing, the light or noise leakage out of the apparatus is eliminated.
Fans are individually provided for other heat generating members including the light source, the power supply, and the ballast, whereby the capacity required for cooling these members is adjusted separately for each member. The air is introduced into the housing by way of the intake air fan, and a portion of the cooling air that has cooled the light valve is absorbed into the cooling fan of the other heat generating member. The other heat generating member is thus cooled, and the cooling air is exhausted out of the apparatus by the exhaust fan. The remainder of the air after cooling the light valve is released out of the apparatus by the exhaust fan through an appropriate path. The light source, the power supply, and the stabilizer have ducts or the like as an outlet of the cooling air in the vicinity of the light source, the power supply and the stabilizer.
By appropriately maintaining the path of the cooling air in the apparatus as described above, the cooling air is efficiently distributed over the heat generating members in the apparatus, so that the heat generating members are efficiently cooled without air stagnation or circulation in the apparatus. The heat generating members are cooled efficiently in this way, and therefore the rotational speed of the fan, i.e. the wind velocity is not increased unnecessarily. Thus the noise of the fan is minimized. The fans other than the intake fan do not propagate the noise directly out of the apparatus. Thus the noise of the apparatus itself can be minimized.